A diver descends from the surface of the sea to the seabed. Explain why the pressure acting on the diver increases as the diver descends.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A scuba diver enters the sea at the surface and swims vertically downwards to the seabed, which is 30 metres below the surface.
Model answer (4 marks)
A greater depth means a greater height of water above the diver, so the weight of that water is larger. The larger weight of water exerts a larger downward force on the diver. Pressure is defined as force divided by area; with the same body area the larger force gives a larger pressure. In a fluid the pressure force acts perpendicular to every surface of the diver, so the pressure increases in all directions as the diver goes deeper.
Examiner tips
- Use the definition of pressure (P=F/A) to link force and pressure.
- Mention that the weight of the overlying water increases with depth.
- Show that the force acts on the diver’s body area, keeping the area constant.
- Include the idea that pressure acts in all directions in a fluid.
Common mistakes
- Confusing pressure with weight or force alone.
- Failing to state that the area of the diver’s body is constant.
- Ignoring that pressure acts perpendicular to all surfaces in a fluid.
Mark scheme (4 marks)
- Greater depth means there is a greater height/weight of fluid (water/sea) above the diver
- The greater weight of water above results in a greater (downward) force on the diver
- Pressure is force divided by area, so a greater force (over the same area of the diver's body) means greater pressure
- The fluid (seawater) exerts a pressure force perpendicular to all surfaces of the diver / pressure acts in all directions in a fluid
Key terms in this question
Related
- All Edexcel GCSE Physics (1PH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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